Magnetic shielding for reducing magnetic interference

ABSTRACT

A magnetic memory array comprises a plurality of magnetic memory cells, a magnetic shielding disposed adjacent to at least one of the magnetic memory cells to reduce magnetic interference with respect to another of the magnetic memory cells, and an insulator disposed as to separate at least a portion of the magnetic shielding from the at least one magnetic memory cell. The magnetic shielding may be a magnetic shield layer, patterned magnetic shield materials, and/or magnetic particles embedded in the insulator.

BACKGROUND

[0001] Generally, a memory chip comprises a plurality of memory cellswhich are etched onto a silicon wafer and addressable via an array ofcolumn conducting leads (bit lines) and row conducting leads (wordlines). That is, the intersection of a bit line and a word linetypically constitutes the address of a memory cell. The memory cells arecontrolled by specialized circuits that perform functions such asidentifying rows and columns of memory cells to read data from or writedata to. Typically, each memory cell stores data in the form of a “1” ora “0,” representing a bit of data.

[0002] An array of magnetic memory cells is often called magnetic randomaccess memory or MRAM. MRAM is generally nonvolatile memory (i.e., asolid state chip that retains data when power is turned off). At leastone type of magnetic memory cell includes a data layer and a referencelayer that is separated from the data layer by an intermediate layer.The data layer may also be referred to as a bit layer, a storage layer,a sense layer, and/or other known terminology. In a magnetic memorycell, a bit of data (e.g., a “1” or “0”) may be stored by “writing” intothe data layer via one or more conducting leads (e.g., a bit line and aword line). The write operation is typically accomplished via a writecurrent that sets the orientation of the magnetic moment in the datalayer to a predetermined direction.

[0003] Once written, the stored bit of data may be read by providing aread current through one or more conducting leads (e.g., a read line) tothe reference layer. In at least one type of magnetic memory cell, theread current sets the orientation of the magnetic moment of thereference layer in a predetermined direction. For each memory cell, theorientations of the magnetic moments of the data layer and the referencelayer are either parallel (in the same direction) or anti-parallel (indifferent directions) to each other. The degree of parallelism affectsthe resistance of the cell, and this resistance can be determined bysensing (e.g., via a sense amplifier) an output current produced by thememory cell in response to the read current.

[0004] More specifically, if the magnetic moments are parallel, theresistance determined based on the output current is of a first relativevalue (e.g., relatively low). If the magnetic moments are anti-parallel,the resistance determined is of a second relative value (e.g.,relatively high). The relative values of the two states (i.e., paralleland anti-parallel) are typically different enough to be senseddistinctly. A “1” or a “0” may be assigned to the respective relativeresistance values depending on design specification.

[0005] In at least one type of magnetic memory cells, the data layer andthe reference layer are implemented using differing magnetic hardnesses.For example, the data layer may be magnetically harder and the referencelayer may be magnetically softer. A harder layer typically has arelatively fixed magnetic state and its magnetic moment is oriented inone direction. It takes a relatively greater current to reverse thedirection of the magnetic moment in a hard layer. The magnetic momentorientation in the soft layer is more readily reversible. Theintermediate layer may comprise a non-magnetic conductive material andis usually thick enough to prevent exchange coupling between the dataand reference layers. The various conducting leads which are used toaddress the memory cells (e.g., bit lines, word lines, and read lines),and to provide currents to pass through the data and reference layers toread data from or write data to the memory cells are provided by one ormore additional layers, called conducting layer(s).

[0006] The layers described above and their respective characteristicsare typical of magnetic memory cells based on tunnelingmagnetoresistance (TMR) effects known in the art. Other combinations oflayers and characteristics may be used to make magnetic memory cellsbased on TMR effects. For example, a pinned reference layer and ananti-ferromagnetic layer may be used in place of the soft referencelayer described above. This configuration of TMR memory cells is wellknown in the art and need not be described in more detail herein. See,for example, U.S. Pat. No. 6,404,674, issued to Anthony et al., andco-pending U.S. application Ser. Nos.: (1) 09/825093, entitled “CladdedRead Conductor For A Pinned-On-The-Fly Soft Reference Layer”, filed onApr. 2, 2001; and (2) 09/963171, entitled “Magneto-Resistive DeviceHaving Soft Reference Layer”, filed on Sep. 25, 2001, which are herebyincorporated by reference in their entirety for all purposes.

[0007] Still other configurations of magnetic memory cells based onother well known physical effects (e.g., giant magnetoresistance (GMR),anisotropic magnetoresistance (AMR), colossal magnetoresistance (CMR),and/or other physical effects) may be implemented with variousembodiments described herein.

[0008] Throughout this application, various exemplary embodiments willbe described in reference to the TMR memory cells having a relativelyhard data layer, and relative soft reference layer, as described above.Those skilled in the art will readily appreciate that the exemplaryembodiments may also be implemented with other types of magnetic memorycells known in the art (e.g., other types of TMR memory cells, GMRmemory cells, AMR memory cells, CMR memory cells, etc.) according to therequirements of a particular implementation.

[0009] Generally speaking, desirable characteristics for anyconfiguration of memory device include increased speed, reduced powerconsumption, and/or lower cost. Lower cost may be achieved by a simplerfabrication process and/or a smaller chip surface area. As the size ofmemory cells is reduced, however, fringe (and/or stray) magnetic fieldsemanating from a target memory cell during a read or write operation maycause increased magnetic interference among neighboring memory cells.Depending on the proximity of magnetic memory cells to each other andthe magnitude of currents being used for read and write operations,fringe magnetic fields may even corrupt a data bit stored in the datalayer of a neighboring magnetic memory cell that was not targeted forthe read or write operations.

[0010] Thus, a market exists for a MRAM device in which fringe magneticfields generated by a magnetic memory cell are materially controlled soas to reduce interference with nearby memory cells. This is especiallyuseful in (although not limited to) high density MRAM devices.

SUMMARY

[0011] In a magnetic memory array comprising a plurality of magneticmemory cells, each of the magnetic memory cells includes a data layerand a reference layer, such that a value stored in the data layer isdeterminable by measuring a relative orientation of the magnetic momentsof the data layer and the reference layer and each magnetic memory cellduring operation emanates fringe magnetic fields potentially influencingnearly magnetic memory cells. An improvement comprises a magneticshielding disposed adjacent to at least one of the magnetic memory cellsto reduce magnetic interference with respect to another of the magneticmemory cells, and an insulator disposed as to separate at least aportion of the magnetic shielding from the at least one magnetic memorycell.

[0012] In various exemplary embodiments to be described herein, themagnetic shielding includes a magnetic shield layer, patterned magneticshield materials, and/or magnetic particles embedded within theinsulating oxide.

[0013] A method for reducing magnetic interference between at least twomemory cells in a magnetic memory array device comprises creating adesired magnetic field within at least one magnetizable layer of a firstmemory cell by providing a current through the layer and reducing anundesirable magnetic interference between the first memory cell and asecond memory cell by absorbing a fringe magnetic field emanating fromthe first memory cell via a magnetic shield material located inproximity to the first memory cell.

BRIEF DESCRIPTION OF THE FIGURES

[0014]FIG. 1 illustrates an array of memory cells in an exemplary MRAMdevice in connection with which the techniques of this patent may beimplemented.

[0015]FIG. 2 illustrates an exemplary magnetic memory cell of theexemplary MRAM device of FIG. 1.

[0016]FIGS. 3a-3 c illustrate MRAM devices having one or more magneticshield layers in accordance with various exemplary embodiments.

[0017]FIGS. 4a-4 c illustrate an exemplary process for forming amagnetic shield layer below the bit plane.

[0018]FIGS. 4d-4 e illustrate an exemplary process for forming amagnetic shield layer on top of the bit plane.

[0019]FIG. 4f illustrates an exemplary process for forming a magneticshield layer both below and on top of the bit plane.

[0020]FIGS. 5a-5 c illustrate patterned magnetic shield materials below,on top of, or in the same plane as the bit plane, respectively.

[0021]FIGS. 5d-5 i illustrate exemplary physical configurations ofpatterned magnetic materials regardless of the plane in which they areimplemented.

[0022]FIGS. 6a-6 d illustrate an exemplary process for forming patternedmagnetic shield materials below the bit plane.

[0023]FIGS. 6e-6 g illustrate an exemplary process for forming patternedmagnetic shield materials above the bit plane.

[0024]FIGS. 7a-7 g illustrate an exemplary process for forming patternedmagnetic shield materials in the same plane as the bit plane.

[0025]FIG. 8 illustrates an exemplary MRAM device having magneticallydoped insulating material between magnetic memory cells.

[0026]FIGS. 9a-9 g illustrate an exemplary process for formingmagnetically doped insulating material between magnetic memory cells.

DETAILED DESCRIPTION

[0027] I. Overview

[0028] Section II describes an exemplary MRAM device, known in thebackground art, in connection with which the various exemplaryembodiments to be described in Sections V, VI, and VII may beimplemented. Section III describes an exemplary memory cell of theexemplary MRAM device. Section IV sets forth the phenomenon of magneticinterference, known in the background art, which is reduced inaccordance with various exemplary embodiments to be described inSections V, VI, and VII. Sections V, VI, and VII illustrate variousexemplary embodiments of techniques for reducing magnetic interference,exemplary MRAM devices using such techniques, and exemplarymanufacturing processes for such devices.

[0029] II. An Exemplary MRAM Device

[0030]FIG. 1 illustrates an exemplary MRAM device 100 including an array110 of magnetic memory cells 120. The magnetic memory cells 120 arearranged in rows and columns, for example, the rows extending along they-axis and the columns extending along the x-axis. In FIG. 1, arepresentative number of magnetic memory cells 120 is shown for ease ofexplanation purposes.

[0031] In FIG. 1, a first conducting layer (comprising word lines) 130extends along the x-axis in the array 110. A second conducting layer(comprising bit lines) 140 extends along the y-axis in the array 1 10.In one embodiment, there is one word line 130 for each row of the array1 10 and one bit line 140 for each column of the array 110. Further, amagnetic memory cell 120 is located at each cross point of a word line130 and a bit line 140. An exemplary TMR magnetic memory cell 120 mayinclude a data layer, a reference layer, and an intermediate layer (aswill be illustrated in greater detail in FIG. 2). In an exemplaryimplementation, the word lines 130 are in contact with data layers ofthe magnetic memory cells 120 and the bit lines 140 are in contact withthe reference layers of the magnetic memory cells 120.

[0032] A third conducting layer (comprising read lines) 150 also extendsalong the y-axis. In an exemplary implementation, the read lines 150 arelocated on top of, and insulated from, the bit lines 140. Alternatively,the read lines 150 may be located beneath the bit lines 140, on top ofor beneath the word lines 130, or any other suitable configurationaccording to device design. Generally, the read lines 150 areindependent of the word lines 130 and bit lines 140.

[0033] The MRAM device 100 also includes circuits such as a first rowdecoder 160 a, a second row decoder 160 b, a first column decoder 170 a,a second column decoder 170 b, and a read/write circuit 180. Theread/write circuit 180 includes a sense amplifier 182, groundconnection(s) 184, a row current source 186, a voltage source 188, and acolumn current source 190.

[0034] A. An Exemplary Write Operation

[0035] During a write operation of a target magnetic memory cell 120,the first row decoder 160 a connects one end of a selected word line 130(i.e., the word line 130 intersecting the target memory cell 120) to therow current source 186, the second row decoder 160 b connects anopposite end of the selected word line 130 to ground, the first columndecoder 170 a connects one end of a selected bit line 140 (i.e., the bitline 140 intersecting the target memory cell 120) to ground 184, and thesecond column decoder 170 b connects the opposite end of the selectedbit line 140 to the column current source 190. As a result, writecurrents flow through the selected word and bit lines 130 and 140. Thewrite currents create magnetic fields, which alter the magneticorientation of the data layer in the target magnetic memory cell 120.

[0036] B. An Exemplary Read Operation

[0037] During a read operation of a target magnetic memory cell 120, thefirst row decoder 160 a connects the voltage source 188 to a selectedword line 130, and the first column decoder 170 a connects a selectedbit line 140 to a virtual ground input of the sense amplifier 182. As aresult, a sense current flows through the target magnetic memory cell120 to the input of the sense amplifier 182. Either before or after theforegoing, the first and second column decoders 170 a and 170 bcooperate to supply a read current through the read line 150intersecting the target magnetic memory cell 120. The read current setsthe magnetic orientation of the reference layer in the target memorycell 120 to a predetermined direction. Then, the resistance state of thetarget magnetic memory cell 150 may be sensed by the sense amplifier182. Thus, the logic state of the target magnetic memory cell 120 isdetermined.

[0038] III. An Exemplary Magnetic Memory Cell

[0039]FIG. 2 illustrates a portion of an exemplary magnetic memory cell120 using TMR effects, and the various layers associated therewith. Thememory cell 120 is accessible via a first conducting layer 210 (or wordline), a second conducting layer 220 (or bit line), and a thirdconducting layer 230 (or read line). The memory cell 120 typicallycomprises a data layer 240, a reference layer 260, and an intermediatelayer 250 (e.g., a tunnel barrier layer) between the data layer 240 andthe reference layer 260. In an exemplary embodiment, the data layer 240and the reference layer 260 are made of ferromagnetic material. The datalayer 240 has a magnetization (represented by the vector M1) that (asillustrated) can be oriented in either of two directions, typicallyalong (i.e., either parallel or antiparallel to) the easy axis (EA1) ofthe data layer 240. The actual direction of the vector will vary fromcell to cell, depending on the value of data bit stored in the cell. Thereference layer 260 has a magnetization (represented by the vector M2)that (as illustrated) can be oriented in either of two directions,typically along its easy axis (EA2). For convenience of illustrationonly, in this exemplary embodiment, the easy axes (EA1, EA2) are shownas extending along the x-axis. If the magnetization vectors (M1 and M2)of the data layer 240 and reference layer 260 are generally pointing inthe same direction, the orientation (or state) of the magnetic memorycell 120 is said to be “parallel.” If the magnetization vectors (M1 andM2) of the data layer 240 and reference layer 260 are generally pointingin opposite directions, the orientation of the magnetic memory cell 120is said to be “anti-parallel.” These two orientations of the data layer240 and reference layer 260, parallel and anti-parallel (as determinedwith respect to each other), are used to represent logic values of “0”and “1,” respectively (or, depending on design choice, “1” and “0”).

[0040] In an exemplary embodiment, the intermediate layer 250 is atunnel barrier layer which may comprise one or more layers of aluminumoxide (Al₂O₃), silicon dioxide (SiO₂), tantalum oxide (Ta₂O₅), siliconnitride (SiN₄), aluminum nitride (AlN), or magnesium oxide (MgO), singlyor in combination. Other dielectrics and/or semiconductor materials mayalso be used for the intermediate layer 250. The thickness of theintermediate layer is determined so as to inhibit exchange couplingbetween the data and reference layers in accordance with the particularelectromagnetic conditions and configuration of the cell in question.For example, in certain commercial exemplary embodiments, theintermediate layer might be about 0.5 nanometers to three nanometersthick.

[0041] Typically, the data layer 240 is magnetically harder than thereference layer 260. For example, in certain commercial implementations,the coercivity of the data layer 240 may be about 2-5 times greater thanthe coercivity of the reference layer 260, although the actual ratiowill be a matter of design choice. The coercivities of the two layers240 and 260 may be different as a result of different physicalconfigurations (e.g., shapes, sizes, geometries, thicknesses, etc.)and/or compositions. In an exemplary embodiment, ferromagnetic materialssuitable for the data layer 240 and the reference layer 260 includenickel iron (NiFe), nickel iron cobalt (NiFeCo), cobalt iron (CoFe),other magnetically soft alloys of NiFe and Co, doped amorphousferromagnetic alloys, PERMALLOY™, and other materials. The data layer240 and the reference layer 260 are not necessarily (and in fact oftenare not) made of the same material.

[0042] In an exemplary embodiment, the first conducting layer 210 is incontact with the data layer 240 and the second conducting layer 220 isin contact with the reference layer 260. In the exemplary embodiment ofFIG. 2, the first and second conducting layers 210 and 220 are shown asbeing orthogonal, which is often a convenient geometric choice. However,this is not necessarily required.

[0043] The location of the third conducting layer 230 is also a matterof design choice. For example, in the exemplary embodiment of FIG. 2,the third conducting layer 230 is located above and insulated from thesecond conducting layer 220. The second and third conducting layers 220and 230 may be separated by an electrical insulator 225 (e.g., a layerof dielectric material). The conducting layers 210, 220 and 230 may bemade of an electrically conductive material such as aluminum, copper,gold, silver, or other materials.

[0044] Data may be written to the magnetic memory cell 120 by supplyingwrite currents to the first and second conducting layers 210 and 220.Typically, a current supplied to the first conducting layer 210 createsa magnetic field about the first conducting layer 210 and a currentsupplied to the second conducting layer 220 creates a magnetic fieldabout the second conducting layer 220. During a write operation, thecombined respective magnetic fields should exceed the coercivity of thedata layer 240 to cause the magnetization vector (M1) of the data layer240 to be set in a desired orientation (such orientation typicallydepends on the direction of the currents being supplied to the first andsecond conducting layers 210 and 220).

[0045] Because the coercivity of the reference layer 260 is typicallyless than that of the data layer 240 (at least in this type of exemplaryTMR memory cell), the combined magnetic fields (about the firstconducting layer 210 and the second conducting layer 220) may cause themagnetization vector (M2) of the reference layer 260 to assume the sameorientation as the magnetization vector (Ml) of the data layer 240.

[0046] When write currents are removed from the first and secondconducting layers 210 and 220, the magnetization vector (M1) of the datalayer 240 generally retains its orientation. However, the magnetizationvector (M2) of the reference layer 260 may or may not retain itsorientation. For example, if the reference layer 260 is “ultrasoft”(i.e., not pinned, or is capable of being “pinned-on-the-fly”) it maylose its magnetization orientation when the write currents are removedfrom the first and second conducting layers 210 and 220. Materials andmethods for making an ultrasoft reference layer are disclosed in U.S.Pat. No. 6,404,674 and co-pending U.S. application Ser. Nos.: (1)09/825093, entitled “Cladded Read Conductor For A Pinned-On-The-Fly SoftReference Layer”, filed on Apr. 2, 2001; and (2) 09/963171, entitled“Magneto-Resistive Device Having Soft Reference Layer”, filed on Sep.25, 2001, which have been incorporated by reference in their entiretyabove.

[0047] Data may be read from the magnetic memory cell 120 by supplying aread current to the third conducting layer 230. Typically, a currentsupplied to the third conducting layer 230 creates a magnetic fieldabout the third conducting layer 230. In an exemplary embodiment, themagnetic field sets the magnetization vector (M2) of the reference layer260 in a desired direction. During a read operation, sense and parasiticcurrents flow through the first and second conducting layers 210 and220, respectively, and may be sensed by the sense amplifier 182 (seeFIG. 1). The resistance in the magnetic cell 120 (i.e., between the datalayer 240 and the reference layer 260) is determined based on thecurrent sensed by the sense amplifier 182, and the logic state is “read”by determining the value of the resistance .

[0048] In an exemplary implementation, the first, second, and thirdconducting layers correspond to the word, bit, and read lines of thedevice, respectively. However, it should be understood that thisparticular correspondence is merely exemplary rather than restrictive.In addition, the labels “first,” “second” and “third” are used forconvenience of discourse, and not intended to denote any particularnumerical quantitative, or other requirement among the various layers.

[0049] Further, the type of magnetic memory cell and its structuredescribed above and illustrated in FIG. 2 (i.e., one type of TMR memorycell) are merely exemplary. Those skilled in the art will appreciatethat other types of memory cells (e.g., GMR memory cells, etc.) as wellas other memory cell structures may used according to the requirementsof a particular implementation. For example, the various layers asillustrated in FIG. 2 may be formed in accordance with othermanufacturing sequences (e.g., the reference layer 260 may be formedbefore the data layer 240), one or more layers may be formed at the sametime, one or more other layers (not shown) may be added or removed, etc.Other types of memory cells and memory cell structures are known in theart and need not be described in more detail herein.

[0050] IV. Fringe Fields Causing Magnetic Interference Among MagneticMemory Cells

[0051] As mentioned earlier, one important design goal in themicroelectronics field generally is to reduce the size ofmicroelectronic devices. The size of a MRAM device may be reduced byplacing the magnetic memory cells 120 closer to each other. However, asthe spacing between magnetic memory cells become smaller, the likelihoodof magnetic interference caused by fringe magnetic fields among thememory cells increase. Depending on the proximity of the memory cells toeach other and the magnitude of applied currents to a target memorycell, fringe magnetic fields emanating from that target memory cell mayeven corrupt a data bit stored in neighboring memory cells.

[0052] As described herein in accordance with various exemplaryembodiments, magnetic shielding (e.g., magnetic shield materials) can beused to reduce or sink (e.g., absorb) such fringe magnetic fields, thusreducing magnetic interference among magnetic memory cells. Somemagnetic shielding might include one or more layers of magneticmaterials such as ferromagnets or ferrites. Examples of ferromagneticmaterials include alloys of nickel (Ni), iron (Fe), and cobalt (Co)(e.g., nickel iron (NiFe), nickel iron cobalt (NiFeCo), cobalt iron(CoFe), other magnetically soft (i.e., having relatively highpermeability) alloys of NiFe and Co, etc.) of various combinations,doped amorphous ferromagnetic alloys, PERMALLOY™, and other materials.Examples of ferrites include ceramic-based magnetic materials. Softferrites are especially beneficial for, although not limited to,high-frequency applications.

[0053] The magnetic shielding may also be referred to as magnetic sink,magnetic shield materials, cladding, field sink, and/or otherterminology. Generally, the amount of magnetic shielding, its physicalconfiguration, and placement adjacent the memory cells depend on themagnitude of the fringe magnetic fields generated at the edges of thememory cells. Thus, the composition, physical configuration, andlocation of magnetic shield materials may be different for differenttypes of memory cells. For example, the composition of the magneticshielding for memory cells with synthetic ferrimagnet layers may bedifferent than the composition of the magnetic shield material formemory cells with ferromagnetic layers (which generate stronger fringemagnetic fields). As used herein, adjacent includes near, next to, closeby, in proximity to, and/or other physical configuration(s) that will beapparent to one skilled in the art.

[0054] Various exemplary embodiments of using magnetic shield materialsto reduce magnetic interference are described below.

[0055] V. An Exemplary Embodiment for Reducing Magnetic Interference

[0056] In one embodiment, a magnetic shield layer is placed either belowor above (or on both sides of) the bit plane. Typically, the magneticshield layer is placed close to the source of fringe magnetic fields(e.g., close to the magnetic memory cells). The bit plane is typicallytaken to be the plane of the magnetic memory cells.

[0057] A. Exemplary MRAM Devices Having One or More Magnetic ShieldLayer(s)

[0058]FIGS. 3a-3 c illustrate, respectively, three exemplary MRAMdevices with magnetic shield layers.

[0059]FIG. 3a illustrates an elevation view of a MRAM device having amagnetic shield layer below the bit plane in accordance with oneexemplary embodiment. FIG. 3a includes a magnetic shield layer 310, aninsulating layer 320 on top of the magnetic shield layer 310, a firstconducting layer 210 on top of the magnetic shield layer 310, multiplememory cells 120 on top of the first conducting layer 210, the secondconducting layer 220 on top of the memory cells 120, an insulating layer225 on top of the second conducting layer 220, and a third conductinglayer 230 on top of the insulating layer 225. In an exemplaryembodiment, the space between one or more of the memory cells 120 isfilled with insulating material 270 (e.g., dielectric material, etc.)that insulates the memory cells from each other. The magnetic shieldlayer 310 may comprise one or more layers of the same or differentferromagnetic material (as disclosed above) or other suitable magneticmaterial.

[0060]FIG. 3b illustrates an elevation view of a MRAM device having amagnetic shield layer above the bit plane in accordance with anotherexemplary embodiment. FIG. 3b includes a first conducting layer 210,multiple memory cells 120 on top of the first conducting layer 210,insulating material 270 between the memory cells 120, a secondconducting layer 220 on top of the memory cells 120, an insulating layer225 on top of the second conducting layer 220, a third conducting layer230 on top of the insulating layer 225, another insulating layer 320 ontop of the third conducting layer 230, and a magnetic shield layer 310on top of the insulating layer 320.

[0061]FIG. 3c illustrates an elevation view of a MRAM device having afirst magnetic shield layer above and a second magnetic shield layerbelow the bit plane in accordance with yet another exemplary embodiment.FIG. 3c includes a first magnetic shield layer 310, an insulating layer320 on top of the first magnetic shield layer, a first conducting layer210, multiple memory cells 120 on top of the first conducting layer 210,insulating material 270 between the memory cells 120, a secondconducting layer 220 on top of the memory cells 120, an insulating layer225 on top of the second conducting layer 220, a third conducting layer230 on top of the insulating layer 225, another insulating layer 320 ontop of the third conducting layer 230, and a second magnetic shieldlayer 310 on top of the insulating layer 320.

[0062] B. Exemplary Processes for Making MRAM Devices Having One or MoreMagnetic Shield Layers

[0063]FIGS. 4a-4 c illustrate an exemplary process for forming amagnetic shield layer below the bit plane. FIGS. 4d-4 e illustrate anexemplary process for forming a magnetic shield layer on top of the bitplane. FIG. 4f illustrates an exemplary process for forming a magneticshield layer both below and on top of the bit plane.

[0064] In FIG. 4a, a magnetic shield layer 410 is formed on a substrate(not shown). In an exemplary embodiment, the magnetic shield layer 410is formed by plasma-assisted deposition, direct-current (DC) orradio-frequency (RF) sputtering, physical vapor deposition, e-beamevaporation, and/or other suitable processes known in the art.Preferably, the magnetic shield layer 410 has high permeability, lowstress, low magnetostriction, high anisotropy (in a known andcontrollable direction), and/or otherwise substantially uniformproperties. The typical thickness of the magnetic shield layer 410 isdetermined so as to reduce fringe magnetic fields without interferingwith normal functions of the memory cells 120 and in accordance with theparticular electromagnetic conditions and configuration of the memorydevice. For example, in an exemplary implementation, the thickness mayrange between 0.5 to 50 nanometers, depending on design requirements.The magnetic shield layer 410 may be formed along the x-axis, they-axis, or other directions depending on design requirements. As shownin FIG. 4a, for convenience of illustration only, the magnetic shieldlayer 410 is formed along the x-axis.

[0065] In FIG. 4b, an insulating layer 420 (e.g., of dielectricmaterial, etc.) is formed on top of the magnetic shield layer 410. In anexemplary embodiment, the insulating layer 420 is formed in accordancewith methods known in the art (e.g., sputtering, vapor depositing, etc.)and its thickness is determined so as to inhibit exchange couplingbetween the magnetic shield layer 410 and the data layers in the memorycells 120. For example, in an exemplary implementation, the thicknessmay range between 20 to 500 nanometers, where a thickness between 50 to100 nanometers is the typical value.

[0066] Next, in FIG. 4c, the first conducting layer 210, magnetic memorycells 120, insulating material 270, second conducting layer 220, aninsulating layer 225, and third conducting layer 230 are formed inaccordance with methods known in the art. For example, the firstconducting layer 210 may be formed using electroplating or othersuitable deposition process then planarized by a planarizing processsuch as chemical mechanical planarization (CMP).

[0067]FIGS. 4d-4 e illustrates an exemplary process for forming themagnetic shield layer 410 on top of the memory cells 120. In thisexemplary process, the insulating layer 420 is first formed on top ofthe third conducting layer 230 as shown in FIG. 4d. In FIG. 4e, themagnetic shield layer 410 is formed on top of the insulating layer 420.

[0068]FIG. 4f illustrates an exemplary process for forming magneticshield layers 410 both below and on top of the memory cells 120. In thisexemplary process, one or more of the processes described above may becombined and implemented to produce the exemplary device shown in FIG.4f. In this Figure, the numbered elements have the same meanings asshown in FIGS. 4a-4 e, and so need not be set forth again.

[0069] In normal configurations of a MRAM device, current-carryingconducting leads (e.g., bit lines, word lines, and read lines) areplaced in close proximity to the memory cells for read and writeoperations. As a result, design constraints may prohibit the use of oneor more magnetic shield layers as disclosed in this embodiment.Exemplary alternative embodiments are thus disclosed below.

[0070] VI. Another Exemplary Embodiment for Reducing MagneticInterference

[0071] In another exemplary embodiment, small amounts of magnetic shieldmaterial are placed in the same or different plane as the bit plane forreducing magnetic interference. In one implementation, one or moremagnetic shield layers as described above are formed, then the magneticshield layers are patterned into small amounts of magnetic shieldmaterials. As explained above, patterned magnetic shield materials maybe preferred over magnetic shield layers as a matter of design choice.The physical configurations (e.g., shape, size, etc.) of the patternedmagnetic shield materials are also determined as a matter of designchoice. For example, the patterned magnetic shield material may formstrips, loops, claddings, crosses, bars, etc. between the memory cells.

[0072] A. Exemplary MRAM Devices Having Patterned Magnetic ShieldMaterials

[0073] Patterned magnetic shield materials may be below, above, or inthe same plane as the bit plane, as illustrated in FIGS. 5a, 5 b, and 5c, respectively.

[0074]FIG. 5a illustrates an elevation view of a MRAM device havingpatterned magnetic shield materials 510 in a plane below the memorycells 120. FIG. 5a includes patterned magnetic shield materials 510,insulating material 520 on top of the patterned magnetic shieldmaterials that optionally insulates the patterned magnetic shieldmaterials 510 from each other, the first conducting layer 210 on top ofthe insulating material 520, multiple memory cells 120 on top of thefirst conducting layer 210, insulating material 270 between the memorycells 120, the second conducting layer 220 on top of the multiple memorycells 120, another insulating layer 225 on top of the second conductinglayer 220, and the third conducting layer 230 on top of the insulatinglayer 225. Generally, the primary purpose of the insulating material 520is to insulate the patterned magnetic shield materials 510 from thefirst conducting layer 210. In addition, the insulating material 520 mayprevent exchange coupling between the patterned magnetic shieldmaterials 510.

[0075] In general, the patterned magnetic shield materials 510 in FIG.5a may overlap with the magnetic memory cells 120 because the patternedmagnetic shield materials 510 are not in the same plane as the magneticmemory cells 120 (i.e., typically no exchange coupling concerns). Theextent of overlap and/or the physical configuration of the patternedmagnetic shield materials are design choices to be made based at leaston the amount and direction of magnetic shielding desired.

[0076]FIG. 5b illustrates an elevation view of a MRAM device havingpatterned magnetic shield materials 510 in a plane above the memorycells 120. FIG. 5b includes the first conducting layer 210 5, multiplememory cells 120 on top of the first conducting layer 210, insulatingmaterial 270 between the memory cells 120, the second conducting layer220 on top of the multiple memory cells 120, an insulating layer 225 ontop of the second conducting layer 220, the third conducting layer 230on top of the insulating layer 225, insulating material 520 on top ofthe third conducting layer 230, and patterned magnetic shield materials510 on top of the insulating material 520. Generally, the primarypurpose of the insulating material 520 is to insulate the patternedmagnetic shield materials 510 from the third conducting layer 230.

[0077] Similar to FIG. 5a, the patterned magnetic shield materials 510in FIG. 5b may generally overlap with the magnetic memory cells 120because the patterned magnetic shield materials 510 are not in the sameplane as the magnetic memory cells 120 (i.e., typically no exchangecoupling concerns). The extent of overlap and/or the physicalconfigurations of the patterned magnetic shield materials are designchoices to be made based at least on the amount and direction ofmagnetic shielding desired.

[0078]FIG. 5c illustrates an elevation view of a MRAM device havingpatterned magnetic shield materials 510 in the same plane as the memorycells 120. FIG. 5c includes the first conducting layer 210, patternedmagnetic shield materials 510 and multiple memory cells 120 in the sameplane on top of the first conducting layer 210, insulating material 270between the memory cells 120 and the patterned magnetic shield materials510, the second conducting layer 220 on top of the multiple memory cells120, another insulating layer 225 on top of the second conducting layer220, and the third conducting layer 230 on top of the insulating layer225. Generally, the primary purpose of the insulating material 270 is toinsulate the memory cells 120 and patterned magnetic shield materials510 from each other to prevent exchange coupling.

[0079] In FIG. 5c, the patterned magnetic shield materials 510 arespaced apart from the magnetic memory cells 120 to prevent exchangecoupling. In an exemplary implementation, spacing (e.g., gaps) betweenthe patterned magnetic shield materials 510 and their respectiveadjacent magnetic memory cells 120 is wide enough to electricallyisolate one from the other. For example, the spacing as implemented maybe approximately 10 nanometers. Of course, smaller (or larger) spacingmay be implemented in accordance with the specific design requirements.

[0080] The patterned magnetic shield materials 510 may or may not be thesame material and/or thickness as the data layers 240 (refer back toFIG. 2) in the memory cells 120. Accordingly, the patterned magneticshield materials 510 may be formed during the same process steps ordifferent process steps of those for forming the data layers 240.

[0081] Whether the patterned magnetic materials are located above, belowor in the same plane as the bit plane, they may be patterned intodifferent shapes depending on design requirements. FIGS. 5d-5 iillustrate exemplary shapes of patterned magnetic materials regardlessof the plane in which they are located. The physical configurations(e.g., shape, size, etc.) of the patterned magnetic shield materials aredesign choices to be made based at least in part on the amount anddirection of magnetic shielding desired.

[0082]FIG. 5d illustrates a plan view of a MRAM device having patternedmagnetic strips 510 located vertically to one side of the memory cells120 in a memory cell array.

[0083]FIG. 5e illustrates a plan view of a MRAM device having patternedmagnetic shield strips 510 located horizontally to one side of thememory cells 120 in a memory cell array.

[0084]FIG. 5f illustrates a plan view of a MRAM device having patternedmagnetic shield loops (e.g., ellipses, ovals, circles, rings, squares,rectangles, etc.) 510 around the memory cells 120 in a memory cellarray. It should be understood that the term “loop” means a closed loopthat is not necessarily circular.

[0085]FIG. 5g illustrates a plan view of a MRAM device having patternedmagnetic shield crosses 510 between the memory cells 120 in a memorycell array.

[0086]FIG. 5h illustrates a plan view of a MRAM device having patternedmagnetic shield strips 510 located horizontally and vertically aroundthe memory cells 120 in a memory cell array.

[0087]FIG. 5i illustrates a plan view of a MRAM device having patternedmagnetic shield bars 510 around the sides of the memory cells 120 in amemory cell array.

[0088] In an exemplary embodiment, the patterned magnetic shieldmaterials 510 are typically insulated from the memory cells 120 by aninsulating material 520, such as dielectric material to prevent exchangecoupling between the memory cells 120 and the patterned magnetic shieldmaterials 510.

[0089] B. Exemplary Processes for Forming Patterned Magnetic ShieldMaterials Below or Above the Bit Plane

[0090]FIGS. 6a-6 d illustrate an exemplary process for forming patternedmagnetic shield materials below the bit plane. FIGS. 6e-6 g illustratean exemplary process for forming patterned magnetic shield materialsabove the bit plane.

[0091] In FIG. 6a, a magnetic shield layer 610 is formed. The magneticshield layer 610 may be formed by methods as described above in FIG. 4a.Next, in FIG. 6b, the magnetic shield layer 610 is patterned to desiredshapes 620 according to design choice (e.g., strips, boxes, loops,crosses, bars, etc.). In an exemplary implementation, the magneticshield layer 610 is patterned using patterning processes known in theart (e.g., coating with photoresist, using appropriate mask and light tocause chemical reaction to desired areas on the layer, stripping certainareas on the layer to leave a desired pattern, etc.). Next, in FIG. 6c,an insulating layer 630 is formed on top of the patterned magneticshield materials 620. In an exemplary implementation, the insulatinglayer 630 may also be patterned (not shown) in accordance with designrequirements. In FIG. 6d, the first conducting layer 210, magneticmemory cells 120, insulating material 270 between the memory cells 120,second conducting layer 220, another insulating layer 225, and thirdconducting layer 230 are formed in accordance with methods known in theart.

[0092]FIGS. 6e-6 g illustrate an exemplary process for forming patternedmagnetic shield materials above the bit plane. Similar to the processesdescribed in FIGS. 4d-4 e, an insulating layer 630 is formed on top ofthe third conducting layer 230 as shown in FIG. 6e. In FIG. 6f, themagnetic shield layer 610 is formed on top of the insulating layer 630.Next, in FIG. 6g, the magnetic shield layer 610 is patterned intovarious shapes 620 in accordance with design choice.

[0093] C. An Exemplary Process for Forming Patterned Magnetic ShieldMaterials in the Same Plane as the Bit Plane

[0094]FIGS. 7a-7 g illustrate an exemplary process for forming patternedmagnetic shield materials in the same plane as the bit plane. In FIG.7a, a first conducting layer 210 is formed. Next, in FIG. 7b, aferromagnetic layer 710 is formed on top of the first conducting layer210. The ferromagnetic layer 710 may comprise one or more layers of thesame or different material depending on design specifications. In FIG.7c, the ferromagnetic layer 710 is patterned to form data layers 240 andmagnetic shield materials 720. The ferromagnetic layer 710 may bedeposited on the first conducting layer 210 via suitable sputteringmethods known in the art or other methods. Next, in FIG. 7d, adielectric layer 730 is formed on top of the data layers 240, themagnetic shield materials 720, and the spaces between them. In anexemplary implementation, the dielectric layer 730 also forms the tunnelbarrier layers 250 and a portion of the insulating material 270 betweenthe memory cells 120.

[0095] In FIG. 7e, another ferromagnetic layer 740 is formed on top ofthe dielectric layer 730. The ferromagnetic layer 740 may comprise oneor more layers of the same or different material depending on designspecifications. In FIG. 7f, the ferromagnetic layer 740 is patterned toform reference layers 260 on top of the data layers (with a layer ofdielectric material in between). Next, in FIG. 7g, insulating material270 is formed on top of the dielectric layer 730 to prevent exchangecoupling between the reference layers 260. Further, in FIG. 7g, thesecond conducting layer 220 is formed on top of the reference layer 260.In an exemplary implementation, the second conducting layer 220 isformed using the same or other method as the first conducting layer 210.Next, an electrically insulating layer 225 is formed on top of thesecond conducting layer 220. Lastly, the third conducting layer 230 isformed on top of the insulating layer 225.

[0096] In another exemplary implementation, the magnetic shieldmaterials 720 may be formed independently from the steps for forming thedata layers 240. Further, the magnetic shield materials 720 may be ofdifferent material, shape, thickness, composition, and/or have othercharacteristics than that of the data layers 240.

[0097] VII. Another Exemplary Embodiment for Reducing MagneticInterference

[0098] In yet another exemplary embodiment, insulating material 270between memory cells 120 is doped with magnetic material. In normalconfigurations of a MRAM device, design constraints may prohibit the useof magnetic shield layers or patterned magnetic shield materials asdisclosed in above exemplary embodiments. Yet another exemplaryalternative embodiment is thus disclosed herein.

[0099] A. An Exemplary MRAM Device Having Magnetically Doped InsulatingMaterial between Magnetic Memory Cells

[0100]FIG. 8 illustrates an exemplary MRAM device having magneticallydoped insulating material 270 between magnetic memory cells. FIG. 8includes multiple memory cells 120 in an array of memory cells that areseparated by dielectric material 270 to prevent exchange couplingbetween the memory cells 120. The dielectric material 270 includesmagnetic particles 810 that are present to reduce fringe magnetic fieldsemanating from either of the adjacent memory cells from interfering withthe other.

[0101] Generally, the amount of the magnetic particles 810 embedded inthe dielectric material 270 should be enough to reduce fringe magneticfields yet not be over-abundant as to render the insulating material 270conducting. Typically, one or more of the soft ferromagnetic materialsas disclosed above may be used in accordance with this exemplaryembodiment.

[0102] B. An Exemplary Process for Forming Magnetically Doped InsulatingMaterial between Magnetic Memory Cells

[0103]FIGS. 9a-9 g illustrate an exemplary process for formingmagnetically doped insulating material between magnetic memory cells.

[0104] In FIG. 9a, the first conducting layer 210 is formed. Next, inFIG. 9b, a ferromagnetic layer 910 is formed on top of the firstconducting layer 910. The ferromagnetic layer 910 may comprise one ormore layers of the same or different material depending on designspecifications. In FIG. 9c, the ferromagnetic layer 910 is patterned toform data layers 240. Next, in FIG. 9d, a dielectric layer 920 is formedon top of the data layers 240. In an exemplary implementation, thedielectric layer 920 covers both the data layers 240 and the areabetween the data layers 240. In this implementation, the dielectriclayer 920 includes some ferromagnetic particles 810. For example, thedielectric layer 920 may be formed via a co-sputtering process in whichferromagnetic material and dielectric material are sputtered at the sametime. In another exemplary implementation, the dielectric layer 920(including some ferromagnetic particles 810) is formed via aco-evaporation process or a plasma oxidation of a deposited metal film.For example, if NiFe, Al, and oxide (O₂) are co-sputtered at the sametime, Al would react with O₂ to form Al₂O₃ with NiFe particles, thus,resulting in a dielectric layer 920 that is doped with NiFe.

[0105] In one instance, the dielectric layer 920 also forms theintermediate layers 250. In another instance, a separate dielectriclayer (not shown) that is undoped with magnetic material may besputtered on top of the dielectric layer 920 to form the intermediatelayers 250. In this latter instance, the dielectric layer 920 shouldpreferably be the same or less in thickness as the data layers 240.

[0106] Next, in FIG. 9e, another ferromagnetic layer 930 is formed ontop of the dielectric layer 920. The ferromagnetic layer 930 maycomprise one or more layers of the same or different material dependingon design specifications. In FIG. 9f, the ferromagnetic layer 930 ispatterned to form reference layers 260 on top of the data layers 240.Next, in FIG. 9g, insulating material 270 is formed on top of thedielectric layer 920 to prevent exchange coupling between the referencelayers 260. In an exemplary implementation, the insulating material 270may also or alternatively be doped with magnetic materials 810 (notshown). Further, in FIG. 9g, the second conducting layer 220 is formedon top of the reference layer 260. An insulating layer 225 is formed ontop of the second conducting layer 220. Lastly, a third conducting layer230 is formed on top of the insulating layer 225.

[0107] VIII. Conclusion

[0108] The various embodiments presented herein include exemplarymagnetic shield configurations for reducing magnetic interference bysubstantially absorbing/shielding unwanted fringe magnetic fields usingmagnetic shielding so that data stored in neighboring magnetic memorycells are not unacceptably corrupted by stray magnetic fields; and alsoexemplary processes for making such configurations.

[0109] Further, the various exemplary embodiments described hereininclude exemplary magnetic shield configurations for implementation withone type of TMR memory cells. Those skilled in the art will appreciatethat the various exemplary magnetic shield configurations may also beimplemented with other types of magnetic memory cells known in the art(e.g., other types of TMR memory cells, GMR memory cells, AMR memorycells, CMR memory cells, etc.) in accordance with the requirements of aparticular implementation.

[0110] The foregoing examples illustrate certain exemplary embodimentsfrom which other embodiments, variations, and modifications will beapparent to those skilled in the art. The inventions should thereforenot be limited to the particular embodiments discussed above, but ratherare defined by the claims.

What is claimed is:
 1. A method for manufacturing a magnetic shield in anon-volatile memory array, said memory array comprising a plurality ofmagnetic memory cells, each of said magnetic memory cells including adata layer and a reference layer, wherein a value stored in said datalayer is determinable by measuring a relative orientation of themagnetic moments of said data layer and said reference layer, at leastone of said magnetic memory cells during operation emanating fringemagnetic fields potentially influencing a nearly magnetic memory cell,said method comprising: (a) forming a magnetic shielding adjacent to atleast one of said magnetic memory cells to reduce magnetic interferencewith respect to another of said magnetic memory cells; and (b) formingan insulator separating at least a portion of said magnetic shieldingfrom said at least one magnetic memory cell.
 2. The method of claim 1where said (a) includes forming said magnetic shielding in the form of alayer.
 3. The method of claim 2 where said magnetic shielding layer isformed above a bit plane of said memory array.
 4. The method of claim 2where said magnetic shielding layer is formed below a bit plane of saidmemory array.
 5. The method of claim 1 where said (a) includes formingsaid magnetic shielding in the form of patterned magnetic shieldmaterials.
 6. The method of claim 5 where a physical configuration of atleast one of said patterned magnetic shield materials is selected basedat least in part on an amount and direction of magnetic shieldingdesired.
 7. The method of claim 5 where said at least one of saidpatterned magnetic shield materials includes a strip.
 8. The method ofclaim 5 where said at least one of said patterned magnetic shieldmaterials includes crosses.
 9. The method of claim 5 where said at leastone of said patterned magnetic shield materials includes bars.
 10. Themethod of claim 5 where said at least one of said patterned magneticshield materials includes loops.
 11. The method of claim 5 where atleast some of said patterned magnetic shield materials are formed in abit plane of said memory array.
 12. The method of claim 5 where at leastsome of said patterned magnetic shield materials are formed in adifferent plane than a bit plane of said memory array.
 13. The method ofclaim 1 where: (1) said magnetic shielding includes a plurality ofmagnetic particles; and (2) said (b) includes: (A) forming an insulatingoxide between some of said magnetic memory cells; and (B) embedding saidplurality of magnetic particles in said insulating oxide.
 14. A methodfor manufacturing a magnetic shield in a magnetic memory array, saidmagnetic memory array comprising a plurality of magnetic memory cells ona substrate, said method comprising: (a) forming at least a portion of amagnetic shield layer: (1) in a different plane than a bit plane of saidmemory array; and (2) adjacent to at least one of said magnetic memorycells to reduce magnetic interference with respect to another of saidmagnetic memory cells; and (b) forming an insulator separating at leasta portion of said magnetic shield layer from said at least one magneticmemory cell.
 15. A method for manufacturing a magnetic shield in amagnetic memory array, said memory array comprising a plurality ofmagnetic memory cells on a substrate, said method comprising: (a)forming patterned magnetic shield materials adjacent to at least one ofsaid magnetic memory cells to reduce magnetic interference with respectto another of said magnetic memory cells; and (b) forming an insulatorseparating at least a portion of said patterned magnetic shieldmaterials from said at least one magnetic memory cell.
 16. A method formanufacturing a magnetic shield in a magnetic memory array, said memoryarray comprising a plurality of magnetic memory cells on a substrate,said method comprising: (a) forming a plurality of magnetic particlesadjacent to at least one of said magnetic memory cells to reducemagnetic interference with respect to another of said magnetic memorycells; and (b) forming an insulator separating at least a portion ofsaid plurality of magnetic shield particles from said at least onemagnetic memory cell: (1) said insulator including an insulating oxidebetween said magnetic memory cells; and (2) said magnetic particlesbeing embedded within said insulating oxide.
 17. A magnetic shield forreducing magnetic interference between at least two magnetic memorycells in a magnetic memory array, said memory array comprising aplurality of magnetic memory cells, each of said magnetic memory cellsincluding a data layer and a reference layer, wherein a value stored insaid data layer is determinable by measuring a relative orientation ofthe magnetic moments of said data layer and said reference layer, atleast one of said magnetic memory cells during operation emanatingfringe magnetic fields potentially influencing a nearly magnetic memorycell, said magnetic shield being made by a process comprising: (a)forming a magnetic shielding adjacent to at least one of said magneticmemory cells to reduce magnetic interference with respect to another ofsaid magnetic memory cells; and (b) forming an insulator separating atleast a portion of said magnetic shielding from said at least onemagnetic memory cell.
 18. A magnetic shield for reducing magneticinterference between at least two magnetic memory cells in a magneticmemory array, said magnetic shield being made by a process comprising:(a) forming a magnetic shield layer: (1) in a different plane than a bitplane of said memory array; and (2) being disposed adjacent to at leastone of said magnetic memory cells to reduce magnetic interference withrespect to another of said magnetic memory cells; and (b) forming aninsulator disposed as to separate at least a portion of said magneticshield layer from said at least one magnetic memory cell.
 19. A magneticshield for reducing magnetic interference between at least two magneticmemory cells in a magnetic memory array, said magnetic shield being madeby a process comprising: (a) forming patterned magnetic shield materialsadjacent to at least one of said magnetic memory cells to reducemagnetic interference with respect to another of said magnetic memorycells; and (b) forming an insulator separating at least a portion ofsaid patterned magnetic shield materials from said at least one magneticmemory cell.
 20. A magnetic shield for reducing magnetic interferencebetween at least two magnetic memory cells in a magnetic memory array,the magnetic shield being made by a method comprising: (a) forming aplurality of magnetic particles adjacent to at least one of saidmagnetic memory cells to reduce magnetic interference with respect toanother of said magnetic memory cells; and (b) forming an insulatordisposed as to separate at least a portion of said plurality of magneticshield particles from said at least one magnetic memory cell: (1) saidinsulator including an insulating oxide between said magnetic memorycells; and (2) said magnetic particles being embedded within saidinsulating oxide.